1. Field of the Invention
The present invention relates to flexible electronic paper. More specifically, the present invention relates to an information device using a plurality of sheets of electronic paper.
2. Description of the Related Art
With the recent advances made towards an information society, a larger volume of text information, image information, and audio information needs to be handled. A variety of information devices that efficiently handle such information have been developed and are commercially available. One of such information devices is an information device called an electronic book. The electronic book is capable of storing and displaying a sufficiently large volume of information as to be physically difficult to store in the form of a traditional book with sheets of paper bound.
A typical electronic book includes a display unit employing a flat panel display, such as a liquid crystal display, and an information holding unit. However, such an electronic book has the limitation that a large amount of page information must be made available on a single display. Thus, the development of easier-to-use information devices or new interfaces has advanced.
A user interface having an additional function of detecting the contact pressure, contact area, contact point, and so forth of a finger touching the display unit of an information device for page updating has been proposed.
Japanese Patent Laid-Open No. 2000-163193 discloses an information device in which it is determined whether or not page scrolling has been input based on a finger touch and the finger movement direction on a display unit such as a liquid crystal display and, if it is determined that page scrolling has been input, the image information being output on the display unit is updated to the image information on the previous or following page.
On the other hand, flexible electronic paper has attracted attention as a new device intended to realize electronic books that provide the feeling of traditional paper bound books. The main goal in the development of electronic paper is as follows:    (1) anytime, anywhere readability and writability;    (2) flexibility in updating text and images;    (3) a viewing screen that causes less visual strain to the human eye (human-eye-friendly screen);    (4) a thin and light body for portability (flexible handling); and    (5) long-term image holding without power.
The development of devices for implementing such flexible electronic paper having the features described above has advanced remarkably.
U.S. Pat. No. 5,724,064 discloses a system including a removable, flexible, induced field activated display sheet with a memory function, a housing having the function of creating appropriate induced fields for activating the sheet to produce an image, and a processor connected to the display sheet for sending image data.
A plurality of sheets of the flexible electronic paper described above are bound into an information device, hereinafter referred to as a flexible electronic book. By giving the feeling of a paper-based book, the flexible electronic book provides better usability than such an electronic book that includes a single flat panel display. However, such a flexible electronic book having a limited number of sheets of flexible electronic paper also requires an interface that allows a large volume of information to be displayed on a limited viewing area. Japanese Patent Laid-Open No. 2002-287729 shows a user interface using an acceleration sensor.
Due to the foregoing problems, there is a need for a flexible electronic book having a plurality of sheets of flexible electronic paper with improved usability in which, particularly, pages can be scrolled as naturally as possible.